CN215444176U - Control valve for a cam phaser of an internal combustion engine - Google Patents

Abstract

A control valve for a cam phaser of an internal combustion engine comprising a cylindrical housing and a control piston arrangement, the housing having a first operating connector, a second operating connector, a supply connector and a tank drain connector for draining hydraulic fluid; the control piston arrangement has a control piston, a supply pipe, a first and a second one-way valve which enable recirculation of cam torque, wherein the control piston arrangement is arranged in a housing and is axially movable by means of an actuator, wherein the first one-way valve is configured with a first and a second valve disc portion and the second one-way valve is configured with a third and a fourth valve disc portion, and the first and the second one-way valve are arranged offset from one another by means of a compression coil spring.

Description

Control valve for a cam phaser of an internal combustion engine

Technical Field

The utility model relates to a control valve for a cam phaser.

Background

Cam phasers are used in valve trains of internal combustion engines in order to be able to variably adjust the phase relationship between the crankshaft and the camshaft in an optimum manner. Thus, a control valve or hydraulic valve is used to control fluid flow between a pressurized fluid supply and the cam phaser and a reservoir or tank. This type of control valve has multiple control positions to facilitate the routing of the fluid flow. Thus, adjustment of the cam phaser to the predetermined phase direction and adjustment of the camshaft to the predetermined phase direction are performed as a function of the control position.

General techniques are known. DE 102013104575a1 describes a hydraulic valve for a cam phaser comprising a sleeve element with a longitudinal channel, a first transverse channel branching off from the longitudinal channel and a second transverse channel branching off from the longitudinal channel, and a pressure-balanced hollow piston arranged axially displaceable within the longitudinal channel between a first end position and a second end position. The longitudinal channel therefore has a first channel section with a larger inner diameter and a second channel section with a smaller inner diameter, wherein the first transverse channel originates from the first channel section and the second transverse channel originates from the second channel section. The hollow piston therefore comprises a longitudinal channel with an axial opening, at least one transverse channel, a first piston section with a larger outer diameter and a second piston section with a smaller outer diameter, wherein the hollow piston is supported at its first piston section at the first channel section of the longitudinal channel with sealing tolerance and at its second piston section at the second channel section of the longitudinal channel with sealing tolerance.

SUMMERY OF THE UTILITY MODEL

The object of the utility model is to improve the control valve described above and to simplify its assembly.

According to one aspect of the utility model, the object is achieved by a control valve for a cam phaser for an internal combustion engine. The control valve includes a cylindrical housing having a first operating connector, a second operating connector, a supply connector, and a tank drain connector configured to drain a hydraulic flow. The control valve further comprises a control piston arrangement having a control piston, a supply pipe, a first one-way valve and a second one-way valve enabling recirculation of cam torque, wherein the control piston arrangement is arranged in the housing to be axially movable by the actuator. Thus, the first check valve is configured with a first valve disc portion and a second valve disc portion, and the second check valve is configured with a first valve disc portion and a second valve disc portion. The one-way valves are arranged to be biased away from each other by a compression coil spring, thereby forming a control chamber between the first valve disc portions. The second valve disc portion is axially movable on the supply pipe. The supply pipe is thus provided with a stop element for limiting the axial movement of the non-return valve in the direction of the control chamber.

The present invention relates to a control valve for a cam phaser for an internal combustion engine, comprising: a cylindrical housing having a first operating fitting, a second operating fitting, a supply fitting, and a tank drain fitting configured to drain a hydraulic flow; a control piston arrangement having a control piston, a supply tube, a first one-way valve and a second one-way valve, the first one-way valve and the second one-way valve enabling cam torque recirculation, wherein the control piston arrangement is arranged in a housing and is axially movable by an actuator, wherein the first one-way valve is provided with a first valve disc portion and a second valve disc portion, and the second check valve is provided with a third valve disc portion and a fourth valve disc portion, and the first and second check valves are arranged to be biased away from each other by a compression coil spring, thereby forming a control chamber between the first and third valve disc portions, wherein the second valve disc portion and the fourth valve disc portion are axially movably arranged on the supply pipe, and wherein the supply pipe is provided with a stop element limiting the axial movement of the first and second one-way valves in the direction towards the control chamber.

In the above control valve, the first check valve and the second check valve are made of light metal or aluminum.

In the above control valve, the stopper member is configured as a portion of the supply pipe having a larger diameter.

In the above-described control valve, the first valve disk section and the third valve disk section are applied in a sealing manner via the respective outer edge to the diameter reduction of the control piston and to a one-way valve seat, and wherein the one-way valve seat is arranged in the control piston.

In the above control valve, the supply pipe comprises at least one inlet opening to the control chamber, wherein the at least one inlet opening is arranged to feed fluid into the control chamber centrally and symmetrically between the first and second one-way valves.

In the above-mentioned control valve, the supply pipe is provided with a hollow cylinder comprising the at least one inlet opening to the control chamber and a connection opening to the supply connection.

In the above control valve, the supply pipe is configured such that the second valve disk portion and the fourth valve disk portion are slidable onto the supply pipe in the axial direction, wherein the compression coil spring is arranged between the first valve disk portion and the third valve disk portion, and an end of the compression coil spring is guided by the valve disk axial protrusion of the first valve disk portion and the valve disk axial protrusion of the third valve disk portion.

In the above-mentioned control valve, the control piston arrangement is movable into a first control position, a second control position and a third control position, wherein in the first control position the first operating joint is closed by the first valve disc portion of the first non-return valve for a fluid flow from the control chamber, wherein by means of the one-way function of the first non-return valve fluid can flow from the first operating joint into the control chamber and to the second operating joint, wherein the first operating joint and the second operating joint are closed in the second control position, and wherein in the third control position the second operating joint is closed by the third valve disc portion of the second non-return valve for a fluid flow from the control chamber, and wherein by means of the one-way function of the second non-return valve fluid can flow from the second operating joint into the control chamber and to the first operating joint.

In the above control valve, the first check valve and the second check valve are axially arranged in the control piston and have opposite opening directions.

In the above control valve, the control valve is provided with a supply connection check valve and a valve disc, and wherein the check valve comprises a circular opening along the centre axis and the check valve comprises an opening in the outer section.

The advantage of the improved control valve is that a simple and low-cost arrangement is combined with a particularly fast camshaft adjustment. This is particularly true if the supply pipe is provided with a stop element for limiting the axial movement of the non-return valve. The control valve according to the utility model is thus configured to be very short or compact in the axial direction, saving space in the combined arrangement with the cam phaser and providing space for new functions as required. This can advantageously ensure that the supply connection remains open during the cam torque recirculation function (CTR).

According to an advantageous embodiment, the non-return valve is made of light metal, preferably aluminium. The non-return valve may also be made of other light materials, such as synthetic materials. Using a lightweight material, such as light metal aluminum, may minimize the moving weight of the check valve and thus accelerate the reaction or response of the check valve. In addition, aluminum, as a very durable and resilient material, provides a very long service life for the check valve.

Furthermore, the stop element is advantageously configured as a portion of the supply tube having a larger diameter. Therefore, the CTR function having the optimal response is ensured simply and at low cost.

Advantageously, the first valve disk section is applied in a sealing manner with its outer edge to the diameter reduction of the control piston and to a one-way valve seat, which is arranged in the control piston. The sealing contact of the first valve disc portion facilitates efficient use of the one-way valve. Thus, the entire fluid flow is directed in a predetermined path and/or direction and unintentional deviation of partial flow is prevented.

Advantageously, the supply pipe comprises at least one inlet opening to the control chamber, wherein the inlet opening is arranged to convey fluid of the control chamber centrally and symmetrically between the one-way valves. The central and symmetrical delivery to the control chamber or to the space between the non-return valves provides a uniform and turbulence-free inflow and/or flow-through of the fluid, regardless of the specific control position of the control valve. This has the advantage that the reaction is faster and the control valve operates constantly and reliably in all possible positions.

The supply pipe is therefore advantageously provided with a hollow cylinder comprising an access opening to the control chamber and a connection port for connection with a supply connection. The connection opening for the supply connection is therefore advantageously arranged at the narrower end of the piston rod. Fluid is led from the supply connection through the connection opening into the hollow cylinder so that the fluid can flow into the control chamber. Thus, a very simple and thus barrier-free and very fast delivery of fluid to the control valve may be provided.

In a particularly advantageous embodiment, the supply pipe is configured such that the second valve disk portion is arranged to be movable onto the supply pipe in the axial direction, wherein the compression coil spring is arranged between the first valve disk portions and the end of the spring is guided by the valve disk axial projection. This optimized design prevents the check valve and spring from tilting or wedging and prevents the check valve from wearing out.

Thus, both check valves operate with the same spring. This arrangement provides a particularly compact and simple configuration of the control piston device. In this case, the number of components is minimized by the springs used in common. Furthermore, since the first and second piston valve discs are identically configured, the complexity and number of components is also minimized. The material and manufacturing costs are significantly reduced.

As in all the preceding and following embodiments, in this embodiment the spring is advantageously configured as a compression coil spring. The compression coil spring is loaded by compressing both ends, wherein the introduction of force is provided by the end coils. The stored energy is released again when the spring is unloaded, pushing the check valve, thereby sealing the piston or valve seat.

According to an advantageous embodiment, the arrangement of the control piston can be moved to a first position and a second position and a third position, and various positions between the first position and the third position.

The non-return valve is thus arranged in the control piston such that in the first position the first operating joint is closed by the first valve disc portion of the first non-return valve with respect to a fluid flow from the control chamber, wherein it is possible for fluid to flow from the first operating joint into the control chamber and to the second operating joint by means of the non-return function of the first non-return valve. Furthermore, two non-return valves are arranged in the control piston, so that in the second position both operating connections are closed. In the third position, the second operating joint is closed by the first valve disc portion of the second one-way valve for fluid flow from the control chamber, wherein fluid flow from the second operating joint into the control chamber and to the first operating joint is possible by the one-way function of the second one-way valve.

With these three positions (also referred to as control positions) the function and purpose of the non-return valve, i.e. the regulation of the fluid flow, can be achieved. As described above, it is possible to adjust the cam phaser and thus the camshaft to a particular phase direction as a function of the control position of the control piston.

According to another advantageous embodiment, the first and second one-way valves are arranged axially in the control piston and have opposite opening directions. The non-return valve is therefore advantageously equipped with identical piston valve disks, which are arranged on the control piston in mirror image with respect to one another.

Drawings

Further advantages of the utility model can be derived from the description and the drawings. The utility model is described in more detail hereinafter with reference to the accompanying drawings, in which:

figure 1 shows a longitudinal section through a first embodiment of a control valve according to the utility model;

fig. 2 shows an enlarged view of a longitudinal section through the control piston device of the control valve of fig. 1;

FIG. 3 illustrates a perspective view of the control valve of FIG. 1;

figure 4 shows a perspective view of the control piston arrangement of figure 2;

FIG. 5 illustrates a perspective view of the check valve and valve disc of the control valve of FIG. 1;

FIG. 6 shows the check valve of FIG. 5;

FIG. 7 shows the valve disc of FIG. 5;

FIG. 8 shows a longitudinal cross-sectional view of the control valve of FIG. 1 with the control piston arrangement in a first position;

FIG. 9 shows a longitudinal cross-sectional view of the control valve of FIG. 1 with the control piston assembly in a second position;

FIG. 10 shows a central longitudinal cross-sectional view of the control valve of FIG. 1 with the control piston arrangement in a third position;

FIG. 11 shows a symbolic view of the control valve of FIG. 1;

fig. 12 shows a longitudinal section through a second embodiment of a control valve according to the utility model.

Detailed Description

The control valves shown in fig. 1 to 12 are used to adjust the path of the fluid flow and thereby produce the phase direction of the cam phaser or its rotor.

Fig. 1 shows a first exemplary embodiment of a control valve 1, which has a cylindrical housing 2, which is configured here as a central screw. The housing 2 comprises a head side 3 and an insertion side 4, wherein a hexagonal head 5 is arranged at the head side 3 and an external thread 6 is arranged at the insertion side 4. Further, the housing 2 includes a plurality of openings provided as a first operation joint a, a second operation joint B, a supply joint P, and a tank discharge joint T. The opening at the insertion side 4 is thus the supply connection P. These openings are arranged in a radially surrounding manner at the housing 2 or in the housing 2 and in the respective series of bores 7, 8, 9. Starting from the insertion side 4, the opening in the first hole row 7 is a tank outlet connection T with an opening 63, in the second hole row 8 the opening 64 is a first operating connection a, and in the third hole row 9 the opening 65 is a second operating connection B. A calibration cap 10 projects from the opening at the insertion side 4, wherein a supply filter 11 is arranged in the calibration cap 10 and is held in the calibration cap 10 by a safety ring 12.

The control valve 1 controls a cam phaser and connects it to a camshaft. This connection is made by screwing of the housing 2 configured as a central bolt and a hexagonal head 5 arranged at the housing 2 and an external thread 6. Control is accomplished through connection A, B, P and T. Thus, fluid is introduced into the control valve 1 through the supply connection P. The operator joints a and B and the fluid flowing out via the operator joint a or the operator joint B facilitate the respective control of the phasing of one of the two operator joints or of the cam phaser. The tank drain connection T is used only for draining excess fluid.

The control valve 1 also comprises a valve disk 13, a supply connection check valve 14, a check valve spring 15, a calibration spring 16 and finally, equally important, a control piston device 17 according to the utility model.

The supply connection check valve 14 is pressed against the valve disk 13 by a check valve spring 15. Check valve 14 opens when the supply pressure acting on valve disc 13 is greater than the spring force and the pressure acting on check valve 14. Fig. 5 to 7 show that the valve disk 13 comprises a circular opening 41 along the center axis of the valve disk 13, while the check valve 14 comprises an outer section opening 42, so that the opening 41 of the valve disk 13 and the opening 42 of the check valve 14 do not overlap in the closed state. This configuration may improve the response of the check valve 14 and, due to the larger opening along the central axis 41, may improve the flow from P. The pressure loss can be further reduced.

The control piston means 17 comprises a control piston 18, a first non return valve 20, a second non return valve 21, a supply pipe 22 and a non return valve seat 19.

The control piston 18 comprises a mounting opening 23 on the head side 3 and a supply opening portion 24 with a supply opening 25 on the insertion side 4. In addition, the control piston 18, like the housing 2 of fig. 1, also has three rows of bores with openings, wherein the rows of bores are configured as a fourth row of bores 26, a fifth row of bores 27 and a sixth row of bores 28. Starting from the insertion side 4, the opening is a first operating through-opening 29 (also called a1) in the fourth row of holes 26, a central through-opening 30 in the fifth row of holes 27 and a second operating through-opening 31 (also called B1) in the sixth row of holes 28.

The check valves 20, 21 enable cam torque recirculation and are best shown in fig. 2, which shows an enlarged control piston arrangement 17 of the control valve 1 of fig. 1. The one-way valve is provided with a first valve disc portion 32, 33, a second valve disc portion 37, 38 and a spring 34 which is thus configured as a compression coil spring. Thus, the first valve disc portion 32 and the second valve disc portion 37 form the first one-way valve 20, and the first valve disc portion 33 and the second valve disc portion 38 form the second one-way valve 21. Thus, at the first valve disk portions 32, 33, the respective outer edges 35, 36 of the first valve disk portions 32, 33 are arranged, which first valve disk portions 32, 33 can be provided with additional radial sealing gaskets or sealing elements at the outer edges 35, 36 in a non-illustrated embodiment. As can be seen from fig. 2, the outer edges 35, 36 are biased towards a reduction 47 in the diameter of the control piston 18 and the one-way valve seat 19, which is fixedly arranged in the control piston 18 at the head side 3.

The inlet opening 44 is arranged in a radially surrounding manner at the hollow supply tube 22. Furthermore, the supply tube 22 ends with a connection opening 45 on the insertion side 4.

Furthermore, a control chamber 46 is visible, which is formed during assembly and is arranged within the control piston 18 between the non-return valves 20, 21 and is traversed by the compression coil spring 34. The control chamber 46 is thus connected in a fluid-conducting manner to a part outside the control piston 18 via the central through-opening 30 and in a fluid-conducting manner to the supply pipe 22 via the inlet opening 44. The supply pipe 22 is thus applied with its connection opening 45 from the inside or from the head side 3 in a form-locking manner to the supply opening portion 24 of the control valve 1.

The second valve disc portions 37, 38 are axially movable on the supply pipe 22, wherein the supply pipe 22 is provided with stop elements 50, 51 for limiting the axial movement of the non-return valves 20, 21 in the direction of the control chamber 46. The control valve 1 according to the utility model is thus configured to be very short or very compact in the axial direction, saving space in the joint arrangement with the cam phaser and providing space for new functions as required. This advantageously ensures that the supply joint P remains open during the cam torque recirculation function (CTR).

Furthermore, the stop elements 50, 51 are advantageously configured as one or two larger diameter portions of the supply tube 22. Therefore, the CTR function having the optimal response is ensured simply and at low cost.

The compression coil spring 34 is arranged between the first valve disc portions 32, 33 and the ends of the spring 34 are guided by disc axial projections 39, 40 which connect the first valve disc portions 32, 33 with the second valve disc portions 37, 38 of the non-return valves 20, 21. This optimized design prevents the check valves 20, 21 and the spring 34 from tilting or wedging and prevents the check valves 20, 21 from wearing out.

Fig. 3 and 4 show perspective views of the control valve 1 and the control piston device 17.

Fig. 8 shows a longitudinal section through the control valve of fig. 1, with the control piston device 17 in a first position 52. The position 52 is illustrated by two arrows pointing towards each other at the tip at the head side 3 of the control valve 1. Since position 52 is a starting position, no movement has yet taken place or the movement of the control piston means 17 in the housing 2 is 0 mm. The arrowhead tips are thus presented in contact with each other. Due to the position 52, three fluid flows 53, 54, 55 are possible in the control valve, wherein these fluid flows are each indicated by a dashed line. These dashed lines are each provided with an arrow at one end to indicate the direction of flow of the fluid streams 53, 54, 55. In particular, a first fluid flow 53 flows from the supply connection P to the second operating connection B, a second fluid flow 54 flows from the first operating connection a to the second operating connection B, and a third fluid flow 55 flows from the first operating connection a to the radially arranged tank drain connection T. For the sake of clarity, reference numeral A, B, P, T is only shown in fig. 2 at the dashed ends representing the fluid streams 53, 54, 55 and/or at the respective corresponding openings at the housing 2. The description used in fig. 2 also applies to the subsequent fig. 3 and 4. The exact path of the fluid streams 53, 55 will be described later.

The first fluid flow 53 flows from the supply connection P through the calibration cap 10 to the supply port portion 24 of the control piston 18 and its supply opening 25. The first fluid flow 53 flows from the supply port portion 24 through the connection port 45 of the supply tube 22 into the hollow cylinder of the supply tube and then through the inlet opening 44 into the control chamber 46. The first fluid flow 53 flows from the control chamber 46 through the central through-opening 30 to the second operational connection B.

The second fluid flow 54 flows from the first operational connection a through the first operational feedthrough 29 and the first one-way valve 20 into the control chamber 46. The second fluid flow 54 flows from the control chamber 46 to the second operational connection B through the central through-opening 30 together with the first fluid flow 53.

The third fluid flow 55 is a simple drain flow, only from the first operating connection a in the housing 2 and the first operating through-opening 29 beyond the control piston 18 to the radially arranged tank drain connection T.

In the illustrated first position 52 of the control piston device 17, the first operating connection a is closed for fluid from the control chamber 46 by the first non-return valve 20. However, it is possible that fluid flows out of the first operation joint a to the control chamber 46 and the second operation joint B by the check valve function of the first check valve 20.

Fig. 9 shows a longitudinal section through the control valve of fig. 1, with the control piston device 17 in a second position 56. In the second position 56, the control piston device 17 is inserted a little further, so that in particular 1.5mm is inserted into the housing 2 in the direction of the insertion side 4. Thus, there is no fluid conducting connection between junction A, B, P and T. The two operating joints A, B are closed due to the axial position of the control piston 18. Thus, no possible fluid flow is shown.

Fig. 10 shows a central longitudinal section through the control valve of fig. 1, with the control piston device 17 in a third position 57. In the third position 57, the control piston device 17 is inserted a little further, in particular an additional insertion of 1.5mm or an overall insertion of 3mm into the housing 2 in the direction of the insertion side 4. Due to the position 57, the three fluid flows 58, 59, 60 that are possible in the control valve are designated herein as a fourth fluid flow 58, a fifth fluid flow 59 and a sixth fluid flow 60. In fig. 10 in particular, a fourth fluid flow 58 flows from the supply connection P to the first operating connection a, a fifth fluid flow 59 flows from the second operating connection B to the first operating connection a and a sixth fluid flow 60 flows from the second operating connection B to a tank outlet connection T arranged at the head side 3. The exact path of the fluid streams 58, 59, 60 will be described later.

As with the first fluid flow 53 of FIG. 2, the fourth fluid flow 58 initially flows from the supply joint P to the control chamber 46. However, the fourth fluid flow 58 flows from the control chamber 46 through the central through-port 30 to the first operational connection A.

A fifth fluid flow 59 flows from the second operating connection B through the second operating through-port 31 and through-port 61 of the one-way valve seat 19 and from there through the second one-way valve 21 into the control chamber 46. A fifth fluid flow 59 flows from the control chamber 46 to the first operational connection a through the central through-opening 30 together with the fourth fluid flow 58.

The sixth fluid flow 30 is a simple drain flow, only from the second operating connection B and through the openings 31, 61 out of the control piston 18 to the tank drain connection T at the head side 3.

In the illustrated third position of the control piston device 17, the second operating joint B is closed by the second non return valve 21 for the fluid supplied through the control chamber 46. However, due to the one-way function of the second one-way valve 21, it is possible for fluid to flow out of the second operating joint B to the control chamber 46 and the first operating joint a.

Fig. 11 shows a symbolic view of the control valve 1 and the three control positions 52, 56, 57. The control valve 1 may be arranged at any position between 52 and 57. Different valve positions control flow by varying the number of exposed orifices. Varying the flow rate can control the speed of the relative position of the camshaft and crankshaft as desired.

Fig. 12 shows a second exemplary embodiment of a control valve 1 having a cylindrical housing 2, which is configured here as a central screw. The control valve differs from the first embodiment only in the design of the one-way valve seat 19, in which an additional valve stem or bolt 62 is fixed. Furthermore, the calibration cap 10 does not protrude from the opening at the insertion side 4.

Claims (10)

1. A control valve for a cam phaser of an internal combustion engine, the control valve comprising:

a cylindrical housing having a first operating fitting, a second operating fitting, a supply fitting, and a tank drain fitting configured to drain a hydraulic flow;

a control piston arrangement having a control piston, a supply tube, a first one-way valve and a second one-way valve, the first one-way valve and the second one-way valve enabling cam torque recirculation,

wherein the control piston device is arranged in a housing and is axially movable by an actuator,

wherein the first one-way valve is provided with a first valve disc portion and a second valve disc portion, and the second one-way valve is provided with a third valve disc portion and a fourth valve disc portion, and the first one-way valve and the second one-way valve are arranged to be biased away from each other by a compression coil spring, thereby forming a control chamber between the first valve disc portion and the third valve disc portion,

wherein the second and fourth valve disk portions are arranged axially movably on the supply pipe and

wherein the supply pipe is provided with a stop element limiting the axial movement of the first and second one-way valves in the direction towards the control chamber.

2. The control valve of claim 1, wherein the first and second check valves are made of light metal or aluminum.

3. The control valve of claim 1, wherein the stop element is configured as a larger diameter portion of the supply tube.

4. The control valve as set forth in claim 1,

characterized in that the first and third valve disk sections are applied in a sealing manner to the diameter reduction of the control piston and to the one-way valve seat via the respective outer edge, and

wherein the one-way valve seat is disposed in the control piston.

5. The control valve as set forth in claim 1,

characterized in that the supply pipe comprises at least one access opening to the control chamber,

wherein the at least one inlet opening is arranged to provide fluid to the control chamber centrally and symmetrically between the first one-way valve and the second one-way valve.

6. Control valve according to claim 5, characterized in that the supply pipe is provided with a hollow cylinder comprising the at least one inlet opening to the control chamber and a connection port to a supply connection.

7. The control valve as set forth in claim 1,

wherein the supply tube is configured such that the second valve disc portion and the fourth valve disc portion are slidable in an axial direction onto the supply tube,

wherein the compression coil spring is disposed between the first valve disc portion and the third valve disc portion, and an end of the compression coil spring is guided by the valve disc axial protrusion of the first valve disc portion and the valve disc axial protrusion of the third valve disc portion.

8. The control valve as set forth in claim 1,

characterized in that the control piston means is movable into a first control position, a second control position and a third control position,

wherein in the first control position the first operating joint is closed by the first valve disc portion of the first one-way valve for fluid flow from the control chamber,

wherein fluid can flow from the first operating joint into the control chamber and to the second operating joint by the one-way function of the first one-way valve,

wherein the first and second operating joints are closed in the second control position, and

wherein in a third control position the second operating joint is closed by the third valve disc portion of the second one-way valve for fluid from the control chamber, and

wherein fluid can flow from the second operating joint into the control chamber and to the first operating joint by the one-way function of the second one-way valve.

9. The control valve of claim 1, wherein the first and second check valves are axially disposed in a control piston and have opposite opening directions.

10. The control valve as set forth in claim 1,

characterized in that the control valve is provided with a supply connection check valve and a valve disc, and

wherein the check valve comprises a circular opening along the central axis and the check valve comprises an opening in the outer section.

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